The cornified envelope of the epidermal keratinocyte is a cross- linked protein structure which provides tensile strength to the stratum corneum and may be altered in some diseases. The research is this proposal will have two major goals. The foremost of these is to examine the hypothesis that the precursor proteins which make up the cornified envelope of the mature keratinocyte are similar across mammalian species and separable into classes based on charge, size, composition, and ability to be cross-linked by the enzyme transglutaminase. This hypothesis will be examined after fulfillment of the second major goal which is to identify, purify, and biochemically characterize the precursor proteins of murine cornified envelope as well as quantitate their contribution to the final product. The latter will be accomplished by generating monoclonal antibodies to whole cornified envelopes and using these antibodies as tools to identify precursors in the soluble and particulate fractions of murine keratinocyte preparations. The proteins will also be identified as transglutaminase substrates by their ability to cross-link with labeled aliphatic amines. Individual precursors will be isolated, purified and biochemically characterized. With this data, the former goal can be realized by direct comparison of biochemical properties between human, bovine, and murine precursors. Also, purified precursors from two species will be mixed with transglutaminase and the resultant reaction products examined for the presence of heteropolymers which would suggest that proteins from one species can functionally substitute for another in cross-linking reactions.